Data Sheet

Freescale Semiconductor
Technical Data
Document Number: MC33975
Rev 11.0, 01/2014
Multiple Switch Detection
Interface with Suppressed
Wake-up and 32 mA Wetting
Current
33975
33975A
MULTIPLE SWITCH
DETECTION INTERFACE WITH
SUPPRESSED WAKE-UP
The 33975 Multiple Switch Detection Interface with Suppressed Wakeup is designed to detect the closing and opening of up to 22 switch
contacts. The switch status, either open or closed, is transferred to the
microprocessor unit (MCU) through a serial peripheral interface (SPI).
The device also features a 22-to-1 analog multiplexer for reading
inputs as analog.
The 33975 device has two modes of operation, Normal and Sleep.
Normal mode allows programming of the device and supplies switch
contacts with pull-up or pull-down current as it monitors the switch
change of state. The Sleep mode provides low quiescent current,
which makes the 33975 ideal for automotive and industrial products
requiring low sleep state currents.
Improvements are a programmable interrupt timer for Sleep mode that
can be disabled, switch detection currents of 32 mA and 4.0 mA for
switch-to-ground inputs, and an interrupt bit that can be reset. This
device is powered using SMARTMOS technology.
Features
Designed to operate from 5.5 V  VPWR  28 V
Switch input voltage: (33975: -14 to 38 V) (33975A: -14 to 40 V)
Interfaces to microprocessor using 3.3 V/5.0 V SPI protocol
Selectable wake-up on change of state
14 switch-to-ground inputs
8 programmable inputs (switches to battery or ground)
Selectable wetting current (32 mA or 4.0 mA for switch-to-ground
inputs)
• Sleep State current VPWR 100 A, VDD 20 A
•
•
•
•
•
•
•
EK SUFFIX (PB-FREE)
98ASA10556D
32-PIN SOICW EP
Applications
• Automotive systems
• Industrial control systems
• Process control systems
• Security systems
• Systems requiring switch status verification for
safety, operation, or process control purposes
VDD
POWER SUPPLY
LVI
VBAT
VBAT
33975
SP0
SP1
VBAT
VPWR
VDD
ENABLE
VDD
SP7
WAKE
SG0
SG1
SG12
SG13
SI
SCLK
CS
SO
INT
AMUX
MCU
MOSI
SCLK
CS
MISO
INT
AN0
WATCHDOG
RESET
GND
Figure 1. 33975 Simplified Application Diagram
© Freescale Semiconductor, Inc., 2005 - 2014. All rights reserved.
1
Orderable Parts
Table 1. Orderable Part Variations
Part Number
MC33975TEK/R2
MC33975ATEK/R2
Temperature (TA)
Package
-40 to 125 °C
32 SOICW-EP
Switch Input Voltage Range
Reference Location
-14 to 38 VDC
5
-14 to 40 VDC
5
33975
2
Analog Integrated Circuit Device Data
Freescale Semiconductor
INTERNAL BLOCK DIAGRAM
INTERNAL BLOCK DIAGRAM
5.0 V
VPWR VPWR
VPWR
SP0
32.0
mA
4.0
mA
16.0
mA
To
+
2.0 4.0 V ‚
SPI
mA Ref
Comparator
POR
Bandgap
Sleep PWR
SP0
SP1
SP2
VPWR
VDD
GND
VPWR, VDD, 5.0V
SP3
SP4
SP5
SP6
VPWR VPWR
32.0
mA
SP7
4.0
mA
5.0 V
Oscillator
and
Clock Control
SP7
16.0
mA
To
+
2.0 4.0 V ‚
SPI
mA Ref
Comparator
VPWR VPWR
32.0
mA
SG0
4.0
mA
VPWR
5.0 V
5.0 V
Temperature
Monitor and
Control
5.0 V
125 k
VPWR
5.0 V
SG0
To
4.0 V ‚+
SPI
Ref
Comparator
SG1
SG2
SG3
WAKE
WAKE Control
VDD
SPI Interface
and Control
SG4
125 k
INT
SG5
INT Control
SG6
VDD
SG7
MUX Interface
SG8
40 A
CS
SG9
SCLK
VDD
SI
SG10
SG11
SG12
VPWR VPWR
32.0
mA
SO
SG13
4.0
mA
SG13
To
4.0 V ‚+
SPI
Ref
Comparator
+
VDD
‚
Analog Mux
Output
AMUX
Figure 2. 33975 Simplified Internal Block Diagram
33975
Analog Integrated Circuit Device Data
Freescale Semiconductor
3
PIN CONNECTIONS
PIN CONNECTIONS
GND
SI
SCLK
CS
SP0
SP1
SP2
SP3
SG0
SG1
SG2
SG3
SG4
SG5
SG6
VPWR
1
32
2
31
3
30
4
29
5
28
6
27
7
26
8
25
9
24
10
23
11
22
12
21
13
20
14
19
15
18
16
17
SO
VDD
AMUX
INT
SP7
SP6
SP5
SP4
SG7
SG8
SG9
SG10
SG11
SG12
SG13
WAKE
Figure 3. 33975 Pin Connections
Table 2. Pin Definitions
A functional description of each Pin can be found in the Functional Pin Description section on page 12.
Pin
Pin Name
Formal Name
Description
1
GND
Ground
2
SI
SPI Slave In
SPI control data input pin from MCU to 33975
3
SCLK
Serial Clock
SPI control clock input pin
4
CS
Chip Select
SPI control chip select input pin from MCU to 33975. Logic [0] allows data to be
transferred in
5–8
25–28
SPn
Programmable Switches 0–3
Programmable Switches 4–7
Programmable switch-to-battery or switch-to-ground input pins
9–15,
18–24
SGn
Switch-to-Ground Inputs 0–6
Switch-to-Ground Inputs 13–7
Switch-to-ground input pins
16
VPWR
Battery Input
Battery supply input pin. This pin requires external reverse battery protection.
17
WAKE
Wake-up
Open drain wake-up output is designed to control a power supply enable pin
29
INT
Interrupt
Open-drain output to MCU is used to indicate input switch change of state
30
AMUX
Analog Multiplex Output
31
VDD
Voltage Drain Supply
32
SO
SPI Slave Out
Ground for logic, analog, and switch-to-battery inputs
Analog multiplex output
3.3/5.0 V supply sets SPI communication level for the SO driver
Provides digital data from 33975 to the MCU
33975
4
Analog Integrated Circuit Device Data
Freescale Semiconductor
ELECTRICAL CHARACTERISTICS
MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
MAXIMUM RATINGS
Table 3. Maximum Ratings
All voltages are with respect to ground unless otherwise noted. Exceeding these limits may cause malfunction or permanent
damage to the device.
Rating
Symbol
Value
Unit
VDD Supply Voltage
–
-0.3 to 7.0
VDC
CS, SI, SO, SCLK, INT, AMUX
–
-0.3 to 7.0
VDC
WAKE
–
-0.3 to 40
VDC
VPWR Supply Voltage
–
-0.3 to 50
VDC
VPWR Supply Voltage at -40 C
–
-0.3 to 45
VDC
Switch Input Voltage Range
–
ELECTRICAL RATINGS
VDC
33975
-14 to 38
33975A
-14 to 40
Frequency of SPI Operation (VDD = 5.0 V)
–
6.0
VESD
±2000
ESD Voltage(1)
MHz
V
Human Body Model(2)
±2000
Applies to all non-input Pins
±200
Machine Model
Charge Device Model
Corner Pins
750
Interior Pins
500
THERMAL RATINGS
C
Operating Temperature
Ambient
TA
-40 to 125
Junction
TJ
-40 to 150
TC
-40 to 125
TSTG
-55 to 150
C
PD
1.7
W
Case
Storage Temperature
Power Dissipation
(3)
Notes
1. ESD testing is performed in accordance with the Human Body Model (CZAP = 100 pF, RZAP = 1500 ), the Machine Model (CZAP =
200 pF, RZAP = 0 ), and the Charge Device Model.
2.
3.
All Programmable Switches (SP) and Switch-to-Ground (SG) input pins when tested individually.
Maximum power dissipation at TJ =150 C junction temperature with no heatsink used.
4.
Thermal resistance between the die and the exposed die pad.
33975
Analog Integrated Circuit Device Data
Freescale Semiconductor
5
ELECTRICAL CHARACTERISTICS
MAXIMUM RATINGS
Table 3. Maximum Ratings
All voltages are with respect to ground unless otherwise noted. Exceeding these limits may cause malfunction or permanent
damage to the device.
Rating
Symbol
Value
Junction to Ambient
RJA
71
Between the die and the exposed die pad(4)
RJC
1.2
TPPRT
Note 6
Unit
ELECTRICAL RATINGS
C/W
Thermal Resistance
Peak Package Reflow Temperature During Reflow(5), (6)
°C
Notes
5. Pin soldering temperature limit is for 10 seconds maximum duration. Not designed for immersion soldering. Exceeding these limits may
cause malfunction or permanent damage to the device.
6. Freescale’s Package Reflow capability meets Pb-free requirements for JEDEC standard J-STD-020C. For Peak Package Reflow
Temperature and Moisture Sensitivity Levels (MSL), Go to www.freescale.com, search by part number [e.g. remove prefixes/suffixes
and enter the core ID to view all orderable parts. (i.e. MC33xxxD enter 33xxx), and review parametrics.
33975
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Analog Integrated Circuit Device Data
Freescale Semiconductor
ELECTRICAL CHARACTERISTICS
STATIC ELECTRICAL CHARACTERISTICS
STATIC ELECTRICAL CHARACTERISTICS
Table 4. Static Electrical Characteristics
Characteristics noted under conditions of 3.0 V  VDD  5.5 V, 8.0 V  VPWR  28 V, -40 C  TC  125 C, unless otherwise
noted. Where applicable, typical values reflect the parameter’s approximate average value with VPWR = 13 V, TA = 25 C.
Characteristic
Symbol
Min
Typ
Max
VPWR(QF)
VPWR(FO)
VPWR(QF)
5.5
–
8.0
8.0
–
28
28
–
38/40
Unit
POWER INPUT
Supply Voltage
V
Supply Voltage Range Quasi-functional(7)
Fully Operational
Supply Voltage Range Quasi-functional
(8)
Supply Voltage
VPWR(POR)
VPWR Supply Voltage Power On Reset
Supply Current
V
4.2
4.6
5.0
–
4.0
8.0
40
70
100
3.0
–
5.5
–
0.25
0.5
–
10
20
12
15
18
7.0
24
9.0
32
–
36
1.8
2.1
2.4
0.5
1.0
–
3.6
4.0
4.4
–
2.0
5.0
IPWR(ON)
All Switches Open, Normal Mode, Tri-state Disabled
Sleep State Supply Current
mA
A
IPWR(SS)
Scan Timer = 64 ms, Switches Open
Logic Supply Voltage
VDD
Logic Supply Current
IDD
All Switches Open, Normal Mode
Sleep State Logic Supply Current
mA
A
IDD(SS)
Scan Timer = 64 ms, Switches Open
V
SWITCH INPUT
Pulse Wetting Current Switch-to-Battery (Current Sink)
IPULSE
5.5 V  VPWR  28 V
Pulse Wetting Current Switch-to-Ground (Current Source)
IPULSE
5.5 V  VPWR  8.0 V
8.0 V  VPWR  28 V
Sustain Current Switch-to-Battery Input (Current Sink)
ISUS(MAX) - ISUS(MIN)
ISUS(MIN)
X 100
mA
ISUSTAIN
5.5 V  VPWR  8.0 V
8.0 V  VPWR  28 V
Sustain Current Matching Between Channels on Switch-to-Ground Inputs
mA
ISUSTAIN
5.5 V  VPWR  28 V
Sustain Current Switch-to-Ground Input (Current Source)
mA
mA
IMATCH
%
Notes
7. Device operational. Wetting and sustain currents are reduced. Operating the analog multiplexer below 8.0 V is not recommended.
8. Thermal considerations must be taken when operating the device above 28 V.
33975
Analog Integrated Circuit Device Data
Freescale Semiconductor
7
ELECTRICAL CHARACTERISTICS
STATIC ELECTRICAL CHARACTERISTICS
Table 4. Static Electrical Characteristics (continued)
Table 4. Static Electrical Characteristics (continued)
Characteristics noted under conditions of 3.0 V  VDD  5.5 V, 8.0 VCharacteristics
 VPWR  28 V,
noted
-40 C
under
 TCconditions
 125 C,ofunless
3.0 V otherwise
 VDD  5.5 V, 8.0 V  VPW
noted. Where
applicable,
typical
values
= 13 reflect
V, TA =the
25parameter’s
C.
approxima
noted. Where applicable, typical values reflect the parameter’s approximate
average
value with
VPWR
Characteristic
SWITCH INPUT (CONTINUED)
Symbol
IOFFSET
Input Offset Voltage when Selected as Analog
VOFFSET
V(SP&SGINPUTS) to AMUX output
Max
Unit
-2.0
1.4
2.0
A
-10
2.5
10
–
10
30
mV
VOL
Sink 250 A
Analog Operational Amplifier Output Voltage
Characteristic
Typ
DIGITAL INTERFACE
Input Offset Current when Selected as Analog
Analog Operational Amplifier Output Voltage
Min
mV
VOH
Source 250 A
V
VDD - 0.1
–
–
Switch Detection Threshold
VTH
3.70
4.0
4.3
V
(9), (10)
TLIM
155
–
185
C
TLIM(HYS)
5.0
10
15
C
Temperature Monitor
Temperature Monitor Hysteresis(10)
Notes
9. Thermal shutdown of 16mA and 32mA pull-up and pull-down current sources only. 4.0mA and 2.0mA current source/sink and all other
functions remain active.
10. This parameter is guaranteed by design; however it is not production tested.
33975
8
Analog Integrated Circuit Device Data
Freescale Semiconductor
Sym
ELECTRICAL CHARACTERISTICS
DYNAMIC ELECTRICAL CHARACTERISTICS
Table 4. Static Electrical Characteristics (continued)
Characteristics noted under conditions of 3.0 V  VDD  5.5 V, 8.0 V  VPWR  28 V, -40 C  TC  125 C, unless otherwise
noted. Where applicable, typical values reflect the parameter’s approximate average value with VPWR = 13 V, TA = 25 C.
Characteristic
Symbol
Min
Typ
Max
Unit
Thresholds(11)
VIH
0.7 x VDD
–
VDD + 0.3
V
Input Logic Low Voltage Thresholds(11)
VIL
GND - 0.3
–
0.2 x VDD
V
Input Logic High Voltage
SCLK, SI, Tri-state SO Input Current
ISCLK, ISI,
ISO(TRI)
0.0 V to VDD
CS Input Current
A
-10
–
10
A
ICS
CS = VDD
CS Pull-up Current
-10
–
10
30
–
100
VDD - 0.8
–
VDD
A
ICS
CS = 0.0 V
SO High State Output Voltage
VSO(HIGH)
I SO(HIGH) = -200 A
SO Low State Output Voltage
V
VSO(LOW)
I SO(HIGH) = 1.6 mA
Input Capacitance on SCLK, SI, Tri-state
SO(12)
–
–
0.4
CIN
–
–
20
pF
–
15
40
100
A
INT Internal Pull-up Current
INT Voltage
V
V INT(HIGH)
INT = Open Circuit
INT Voltage
V
VDD - 0.5
–
VDD
–
0.2
0.4
20
40
100
4.0
4.3
5.3
V INT(LOW)
I INT = 1.0 mA
WAKE Internal Pull-Up current
I WAKE(PU)
WAKE Voltage
V
V WAKE (HIGH)
WAKE = Open Circuit
WAKE Voltage
V
V WAKE(LOW)
I WAKE = 1.0 mA
V
–
WAKE Voltage(12)
0.2
0.4
V WAKE(MAX)
Maximum Voltage Applied to WAKE Through External Pull-up
A
V
–
–
40
Notes
11. Upper and lower logic threshold voltage levels apply to SI, CS, and SCLK.
12. This parameter is guaranteed by design however, is not production tested.
DYNAMIC ELECTRICAL CHARACTERISTICS
Table 5. Dynamic Electrical Characteristics
Characteristics noted under conditions of 3.0V  VDD  5.5V, 8.0V  VPWR  28V, -40C  TC  125C, unless otherwise noted.
Where applicable, typical values reflect the parameter’s approximate average value with VPWR = 13 V, TA = 25C.
Characteristic
Symbol
Min
Typ
Max
Unit
SWITCH INPUT
33975
Analog Integrated Circuit Device Data
Freescale Semiconductor
9
ELECTRICAL CHARACTERISTICS
DYNAMIC ELECTRICAL CHARACTERISTICS
Table 5. Dynamic Electrical Characteristics
Characteristics noted under conditions of 3.0V  VDD  5.5V, 8.0V  VPWR  28V, -40C  TC  125C, unless otherwise noted.
Where applicable, typical values reflect the parameter’s approximate average value with VPWR = 13 V, TA = 25C.
Characteristic
Symbol
Min
Typ
Max
Unit
t PULSE (ON)
15
16
22
ms
–
5.0
16
100
200
300
–
–
10
–
–
10
–
–
10
100
–
–
50
–
–
16
–
–
20
–
–
t R (SI)
–
5.0
–
ns
t F (SI)
–
5.0
–
ns
Time from Falling Edge of CS to SO Low Impedance(16)
t SO(EN)
–
–
55
ns
Impedance(17)
t SO(DIS)
–
–
55
ns
t VALID
–
25
55
ns
Pulse Wetting Current Time
Interrupt Delay Time
s
t INT-DLY
Normal Mode
Sleep Mode Switch Scan Time
t SCAN
Calibrated Scan Timer Accuracy
t SCAN TIMER
Sleep Mode
Calibrated Interrupt Timer Accuracy
%
t INT TIMER
Sleep Mode
s
%
DIGITAL INTERFACE TIMING(13)
Required Low State Duration on VPWR for Reset(14)
Falling Edge of CS to Rising Edge of SCLK
t LEAD
Required Setup Time
Falling Edge of SCLK to Rising Edge of CS
Falling Edge of SCLK to SI
SI, CS, SCLK Signal Rise Time(15)
Time(15)
Time from Rising Edge of SCLK to SO Data Valid(18)
Notes
13.
14.
15.
16.
17.
18.
ns
t SI(HOLD)
Required Hold Time
Time from Rising Edge of CS to SO High
ns
t SI(SU)
Required Setup Time
SI, CS, SCLK Signal Fall
ns
t LAG
Required Setup Time
SI to Falling Edge of SCLK
s
t RESET
VPWR  0.2V
ns
These parameters are guaranteed by design. Production test equipment uses 4.16 MHz, 5.0V SPI interface.
This parameter is guaranteed by design but not production tested.
Rise and Fall time of incoming SI, CS, and SCLK signals suggested for design consideration to prevent the occurrence of double pulsing.
Time required for valid output status data to be available on the SO pin.
Time required for output states data to be terminated at the SO pin.
Time required to obtain valid data out from SO following the rise of SCLK with a 200pF load.
33975
10
Analog Integrated Circuit Device Data
Freescale Semiconductor
ELECTRICAL CHARACTERISTICS
TIMING DIAGRAMS
TIMING DIAGRAMS
CS
0.2 VDD
tLEAD
tLAG
0.7 VDD
0.2 VDD
SCLK
tSI(SU) tSI(HOLD)
0.7 VDD
0.2 VDD
SI
MSB in
tSO(EN)
tVALID
0.7 VDD
0.2 VDD
SO
tSO(DIS)
MSB out
LSB out
Figure 4. SPI Timing Characteristics
VPWR
VDD
WAKE
Wake-Up From Interrupt
Timer Expire
INT
CS
Wake-Up From
Closed Switch
SGn
Power-Up
Normal Mode
Tri-State
Command
Sleep
Command
Sleep Mode
(Disable Tri-State)
Normal
Mode
Sleep Command
Sleep Mode
Normal
Mode
Sleep Command
Figure 5. Sleep Mode to Normal Mode Operation
INT
CS
Switch state change with
Switch state change with
CS low generates INT
CS low generates INT
Latch switch status
on falling edge of CS
Rising edge of CS does not
clear INT because state change
occurred while CS was low
SGn
Switch open ‚Äö
Switch closed ‚Äö
SGn Bit in SPI Word
1
Switch
Status
Command
0
Switch
Status
Command
0
Switch
Status
Command
1
Switch
Status
Command
1
Switch
Status
Command
0
Switch
Status
Command
Figure 6. Normal Mode Interrupt Operation
33975
Analog Integrated Circuit Device Data
Freescale Semiconductor
11
FUNCTIONAL DESCRIPTIONS
INTRODUCTION
FUNCTIONAL DESCRIPTIONS
INTRODUCTION
The 33975 device is an integrated circuit designed to provide
systems with ultra-low quiescent sleep/wake-up modes and
a robust interface between switch contacts and a
microprocessor. The 33975 replaces many of the discrete
components required when interfacing to microprocessorbased systems while providing switch ground offset
protection, contact wetting current, and system wake-up.
The 33975 features 8-programmable switch-to-ground or
switch-to-battery inputs and 14 switch-to-ground inputs. All
switch inputs may be read as analog inputs through the
analog multiplexer (AMUX). Other features include a
programmable wake-up timer, programmable interrupt timer,
programmable wake-up/interrupt bits, and programmable
wetting current settings.
This device is designed primarily for automotive applications
but may be used in a variety of other applications such as
computer, telecommunications, and industrial controls.
FUNCTIONAL PIN DESCRIPTION
CHIP SELECT (CS)
SERIAL INPUT (SI)
The system MCU selects the 33975 to receive
communication using the chip select (CS) pin. With CS in a
logic low state, command words may be sent to the 33975 via
the serial input (SI) pin, and switch status information can be
received by the MCU via the serial output (SO) pin. The
falling edge of CS enables the SO output, latches the state of
the INT pin, and the state of the external switch inputs.
Rising edge of the CS initiates the following sequence:
The SI pin is used for serial instruction data input. SI
information is latched into the input register on the falling
edge of SCLK. A logic high state present on SI will program
a one in the command word on the rising edge of the CS
signal. To program a complete word, 24 bits of information
must be entered into the device.
1. Disables the SO driver (high-impedance)
2. INT pin is reset to logic [1], except when additional
switch changes occur during CS low (see Figure 6,
page 11).
3. Activates the received command word, allowing the
33975 to act upon new data from switch inputs.
To avoid any spurious data, it is essential the high-to-low and
low-to-high transitions of the CS signal occur only when
SCLK is in a logic low state. A clean CS signal is needed to
ensure no incomplete SPI words are sent to the device.
Internal to the 33975 device is an active pull-up to VDD on CS.
In Sleep Mode the negative edge of CS (VDD applied) will
wake up the 33975 device. Data received from the device
during CS wake-up may not be accurate.
SERIAL CLOCK (SCLK)
The system clock (SCLK) pin clocks the internal shift register
of the 33975. The SI data is latched into the input shift
register on the falling edge of SCLK signal. The SO pin shifts
the switch status bits out on the rising edge of SCLK. The SO
data is available for the MCU to read on the falling edge of
SCLK. False clocking of the shift register must be avoided to
ensure validity of data. It is essential the SCLK pin be in a
logic low state whenever CS makes any transition. For this
reason, it is recommended, though not necessary, that the
SCLK pin is commanded to a low logic state as long as the
device is not accessed and CS is in a logic high state. When
the CS is in a logic high state, any signal on the SCLK and SI
pin will be ignored and the SO pin is tri-state.
SERIAL OUTPUT (SO)
The SO pin is the output from the shift register. The SO pin
remains tri-stated until the CS pin transitions to a logic low
state. All open switches are reported as a zero, all closed
switches are reported as a one. The negative transition of CS
enables the SO driver.
The first positive transition of SCLK will make the status data
bit 24 available on the SO pin. Each successive positive clock
will make the next status data bit available for the MCU to
read on the falling edge of SCLK. The SI/SO shifting of the
data follows a first-in-first-out protocol, with both input and
output words transferring the most significant bit (MSB) first.
INTERRUPT OUTPUT (INT)
The INT pin is an interrupt output from the 33975 device. The
INT pin is an open-drain output with an internal pull-up to
VDD. In Normal mode, a switch state change will trigger the
INT pin (when enabled). The INT pin is latched on the falling
edge of CS, and cleared on the rising edge of CS. The INT pin
will not clear with rising edge of CS if a switch contact change
has occurred while the CS was low.
In a multiple 33975 device system with WAKE high and VDD
in (Sleep mode), the falling edge of INT will place all 33975s
in Normal mode.
WAKE INPUT (WAKE)
The WAKE pin is an open-drain output and a wake-up input.
The pin is designed to control a power supply Enable pin. In
the Normal mode, the WAKE pin is low. In the Sleep mode,
the WAKE pin is high. The WAKE pin has a pull-up to the
internal +5.0 V supply.
33975
12
Analog Integrated Circuit Device Data
Freescale Semiconductor
FUNCTIONAL DESCRIPTIONS
FUNCTIONAL PIN DESCRIPTION
In Sleep mode with the WAKE pin high, the falling edge of
WAKE will place the 33975 in Normal mode. In Sleep mode
with VDD applied, the INT pin must be high for a negative
edge of WAKE to wake up the device. If VDD is not applied to
the device in Sleep mode, INT does not affect the WAKE
operation.
LOAD SUPPLY VOLTAGE (VPWR)
The VPWR pin is battery input and Power-ON Reset to the
33975 IC. The VPWR pin requires external reverse battery
and transient protection. The maximum input voltage on
VPWR is 50 V. All wetting, sustain, and internal logic current is
provided from the VPWR pin.
LOGIC VOLTAGE (VDD)
The VDD input pin is used to determine logic levels on the
microprocessor interface (SPI) pins. Current from VDD is
used to drive the SO output, and the pull-up current for CS
and INT pins. VDD must be applied for a wake-up from the
negative edge of CS or INT.
GROUND (GND)
The GND pin provides ground for the IC as well as ground for
inputs programmed as switch-to-battery inputs.
PROGRAMMABLE SWITCHES (SP0–SP7)
The 33975 device has 8 switch inputs capable of being
programmed to read switch-to-ground or switch-to-battery
contacts. The input is compared with a 4.0 V reference.
When programmed to be switch-to-battery, voltages greater
than 4.0 V are considered closed. Voltages less than 4.0 V
are considered open. The opposite holds true when inputs
are programmed as switch-to-ground. Programming features
are defined in Table 6 through Table 11 in the Functional
Device Operation section of this datasheet beginning on
page 16. Voltages greater than the VPWR supply voltage will
source current through the SP inputs to the VPWR pin.
Transient battery voltages greater than 38/40 V must be
clamped by an external device.
SWITCH-TO-GROUND (SG0–SG13)
The SGn pins are switch-to-ground inputs only. The input is
compared with a 4.0 V reference. Voltages greater than 4.0 V
are considered open. Voltages less than 4.0 V are
considered closed. Programming features are defined in
Table 6 through Table 11 in the Functional Device Operation
section of this datasheet beginning on page 16. Voltages
greater than the VPWR supply voltage will source current
through the SG inputs to the VPWR pin. Transient battery
voltages greater than 38/40 V must be clamped by an
external device.
33975
Analog Integrated Circuit Device Data
Freescale Semiconductor
13
FUNCTIONAL DESCRIPTIONS
FUNCTIONAL INTERNAL BLOCK DESCRIPTION
FUNCTIONAL INTERNAL BLOCK DESCRIPTION
MC33975 - Functional Block Diagram
Analog Control
and Protection Circuitry
Bandgap
Voltage Regulation
Temp. Sense
Oscillator & Clock
MCU Interface and Control
Interrupt/Wake-up
SPI Interface
Programmable
Monitor Inputs
SP0 - SP7
Monitor Inputs
SG0 - SG13
Multiplex Control
Control & Protection
Interface & Control
Prog. Monitor
Monitor
Figure 7. Functional Internal Block Description
ANALOG CONTROL AND PROTECTION
CIRCUITRY:
The 33975 is designed to operate from 5.5 V to 38/40 V on
the VPWR pin. Characteristics are provided from 8.0 to 28 V
for the device. Switch contact currents and the internal logic
supply are generated from the VPWR pin. The VDD supply
pin is used to set the SPI communication voltage levels,
current source for the SO driver, and pull-up current on INT
and CS.
The on-chip voltage regulator and bandgap supplies the
required voltages to the internal monitor circuitry. The
temperature monitor is active in the Normal Mode.
MCU INTERFACE AND CONTROL:
The 33975 Multiple Switch Detection Interface with
Suppressed Wake-up is designed to detect the closing and
opening of up to 22 switch contacts. The switch status, either
open or closed, is transferred to the microprocessor unit
(MCU) through a serial peripheral interface (SPI).
The device also features a 22-to-1 analog multiplexer for
reading inputs as analog. The 33975 device has two modes
of operation, Normal and Sleep.
SWITCH PROGRAMMABLE INPUTS:
Programmable switch detection inputs. These 8 inputs can
selectively detect switch closures to ground or battery. The
33975 device has 8 switch inputs capable of being
programmed to read switch-to-ground or switch-to-battery
contacts. The input is compared with a 4.0 V reference.
When programmed to be switch-to-battery, voltages greater
than 4.0 V are considered closed. Voltages less than 4.0 V
are considered open. The opposite holds true when inputs
are programmed as switch-to-ground.
SWITCH–TO-GROUND INPUTS:
Switch detection interface inputs. These 14 inputs can detect
switch closures to ground only. The input is compared with a
4.0 V reference. Voltages greater than 4.0 V are considered
open. Voltages less than 4.0 V are considered closed. Note:
Each of these inputs may be used to supply current to
sensors external to a module.
33975
14
Analog Integrated Circuit Device Data
Freescale Semiconductor
FUNCTIONAL DESCRIPTIONS
FUNCTIONAL INTERNAL BLOCK DESCRIPTION
MCU INTERFACE DESCRIPTION
The 33975 device directly interfaces to a 3.3 or 5.0 V
microcontroller unit (MCU). SPI serial clock frequencies up to
6.0 MHz may be used for programming and reading switch
input status (production tested at 4.16 MHz). Figure 8
illustrates the configuration between an MCU and one 33975.
Serial peripheral interface (SPI) data is sent to the 33975
device through the SI input pin. As data is being clocked into
the SI pin, status information is being clocked out of the
device by the SO output pin. The response to a SPI
command will always return the switch status, reset flag, and
thermal flag. Input switch states are latched into the SO
register on the falling edge of the chip select (CS) pin.
Twenty-four bits are required to complete a transfer of
information between the 33975 and the MCU.
MC68HCXX
Microcontroller
33975
MOSI
SI
Shift Register
MISO
SCLK
Parallel
Ports
SO
SCLK
CS
INT
INT
33975
SI
SO
SCLK
MC68HCXX
Microcontroller
Shift Register
INT
MOSI
SI
MISO
SO
24-Bit Shift Register
SCLK
Figure 9. SPI Parallel Interface with Microprocessor
MC68HCXX
Microcontroller
Receive
Buffer
To Logic
CS
Parallel
Ports
CS
33975
INT
INT
Figure 8. SPI Interface with Microprocessor
Two or more 33975 devices may be used in a module
system. Multiple ICs may be SPI-configured in parallel or
serial. Figures 9 and 10 show the configurations. When using
the serial configuration, 48-clock cycles are required to
transfer data in/out of the ICs.
33975
MOSI
SI
Shift Register
MISO
SCLK
Parallel
Ports
INT
SO
SCLK
CS
INT
33975
SI
SO
SCLK
CS
INT
Figure 10. SPI Serial Interface with Microprocessor
33975
Analog Integrated Circuit Device Data
Freescale Semiconductor
15
FUNCTIONAL DEVICE OPERATION
OPERATIONAL MODES
FUNCTIONAL DEVICE OPERATION
POWER SUPPLY
POWER-ON RESET (POR)
The 33975 is designed to operate from 5.5 to 38/40 V on the
VPWR pin. Characteristics are provided from 8.0 to 28 V for
the device. Switch contact currents and the internal logic
supply are generated from the VPWR pin. The VDD supply
pin is used to set the SPI communication voltage levels,
current source for the SO driver, and pull-up current on INT
and CS.
VDD supply may be removed from the device to reduce
quiescent current. If VDD is removed while the device is in
Normal mode, the device will remain in Normal mode. If VDD
is removed in Sleep mode, the device will remain in Sleep
mode until a wake-up input is received (WAKE high to low,
switch input or interrupt timer expires).
Removing VDD from the device disables SPI communication
and will not allow the device to wake up from the INT and CS
pins.
Applying VPWR to the device will cause a Power-ON Reset
and place the device in Normal mode.
Default settings from Power-ON Reset via a VPWR or Reset
Command are as follows:
• Programmable switch – Set to switch-to-battery
• All inputs set as wake-up
• Wetting current on (16 mA pull-down, 32 mA pull-up)
• Wetting current timer on (20 ms)
• All inputs tri-state
• Analog select 00000 (no input channel selected)
Note The 33975 device provides indication that a reset has
occurred by placing a logic [1] in bit 22 of the SO buffer. The
reset bit is cleared on rising edge of CS.
OPERATIONAL MODES
• Tri-state Register (Tri-state Command)
• Analog Select Register (Analog Command)
• Calibration of Timers (Calibration Command)
• Reset (Reset Command)
Figure 6, page 11, is a graphical description of the device
operation in Normal mode. Switch states are latched into the
input register on the falling edge of CS. The INT to the MCU
is cleared on the rising edge of CS. However, INT will not
clear on the rising edge of CS if a switch has closed during
SPI communication (CS low). This prevents switch states
from being missed by the MCU.
The 33975 has two operating modes, Normal mode and
Sleep mode. A discussion on Normal mode begins below. A
discussion on Sleep Mode begins on page 21.
NORMAL MODE
Normal mode may be entered by the following events:
• Application of VPWR to the IC
• Change-of-switch state (when enabled)
• Falling edge of WAKE
• Falling edge of INT (with VDD = 5.0 V and WAKE at
Logic [1])
• Falling edge of CS (with VDD = 5.0 V)
• Interrupt timer expires
Only in Normal mode with VDD applied can the registers of
the 33975 be programmed through the SPI.
The registers that may be programmed in Normal mode are
listed below. Further explanation of each register is provided
in subsequent paragraphs.
• Programmable Switch Register (Settings Command)
• Wake-up/Interrupt Register (Wake-up/Interrupt
Command)
• Wetting Current Register (Metallic Command)
• Wetting Current Timer Register (Wetting Current Timer
Enable Command)
PROGRAMMABLE SWITCH REGISTER
Inputs SP0 to SP7 may be programmable for switch-tobattery or switch-to-ground. These inputs types are defined
using the settings command (refer to Table 6). To set an SPn
input for switch-to-battery, a logic [1] for the appropriate bit
must be set. To set an SPn input for switch-to-ground, a
logic [0] for the appropriate bit must be set. The MCU may
change or update the Programmable Switch Register via
software at any time in Normal mode. Regardless of the
setting, when the SPn input switch is closed a logic [1] will be
placed in the Serial Output Response Register (refer to
Table 17, page 21).
Table 6. Settings Command
Settings Command
Not used
Battery/Ground Select
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
1
X
X
X
X
X
X
X
X
sp7
sp6
sp5
sp4
sp3
sp2
sp1
sp0
33975
16
Analog Integrated Circuit Device Data
Freescale Semiconductor
FUNCTIONAL DEVICE OPERATION
OPERATIONAL MODES
WAKE-UP/INTERRUPT REGISTER
IC in Sleep mode (refer to Table 7). Programming the wakeup/interrupt bit to logic [1] will enable the specific input to
generate an interrupt with switch change of state and will
enable the specific input as wake-up. The MCU may change
or update the Wake-up/Interrupt Register via software at any
time in Normal mode.
The Wake-up/Interrupt Register defines the inputs that are
allowed to wake the 33975 from Sleep mode or set the INT
pin low in Normal mode. Programming the wake-up/interrupt
bit to logic [0] will disable the specific input from generating
an interrupt and will disable the specific input from waking the
Table 7. Wake-Up /Interrupt Command
Wake-up/Interrupt Command
Command Bits
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
0
0
0
0
0
0
1
0
X
X
X
X
X
X
X
X
sp7
sp6
sp5
sp4
sp3
sp2
sp1
sp0
0
0
0
0
0
0
1
1
X
X
sg1
3
sg1
2
sg1
1
sg1
0
sg9
sg8
sg7
sg6
sg5
sg4
sg3
sg2
sg1
sg0
WETTING CURRENT REGISTER
The 33975 has two levels of switch-to-ground contact
current, 32 and 4.0 mA, and two levels of switch-to-battery
contact current, 16 and 2.0 mA (see Figure 11). The metallic
command is used to set the switch contact current level (refer
to Table 8). Programming the metallic bit to logic [0] will set
the switch wetting current to 2.0 mA/4.0 mA. Programming
the metallic bit to logic [1] will set the switch contact wetting
current to 16 mA/32 mA. The MCU may change or update the
Wetting Current Register via software at any time in Normal
Mode.
Wetting current is designed to provide higher levels of current
during switch closure. The higher level of current is designed
to keep switch contacts from building up oxides that form on
the switch contact surface.
Switch Contact Voltage
32 mA Switch Wetting Current
4.0 mA Switch Sustain Current
20 ms Wetting Current Timer
Figure 11. Contact Wetting and Sustain Current
for Switch-to-Ground Input
Table 8. Metallic Command
Metallic Command
Command Bits
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
0
0
0
0
0
1
0
0
X
X
X
X
X
X
X
X
sp7
sp6
sp5
sp4
sp3
sp2
sp1
sp0
0
0
0
0
0
1
0
1
X
X
sg1
3
sg1
2
sg1
1
sg1
0
sg9
sg8
sg7
sg6
sg5
sg4
sg3
sg2
sg1
sg0
WETTING CURRENT TIMER REGISTER
Each switch input has a designated 20 ms timer. The timer
starts when the specific switch input crosses the comparator
threshold (4.0 V). When the 20 ms timer expires, the contact
current is reduced from 16 to 2.0 mA for switch-to-battery
inputs and 32 to 4.0 mA for switch-to-ground inputs. The
wetting current timer may be disabled for a specific input.
When the timer is disabled, wetting current will continue to
flow through the closed switch contact. With multiple wetting
current timers disabled, power dissipation for the IC must be
considered.
The MCU may change or update the Wetting Current Timer
Register via software at any time in Normal mode. This allows
the MCU to control the amount of time wetting current is
applied to the switch contact. Programming the wetting
current timer bit to logic [0] will disable the wetting current
timer. Programming the wetting current timer bit to logic [1]
will enable the wetting current timer (refer to Table 9).
33975
Analog Integrated Circuit Device Data
Freescale Semiconductor
17
FUNCTIONAL DEVICE OPERATION
OPERATIONAL MODES
Table 9. Wetting Current Timer Enable Command
Wetting Current Timer Commands
Command Bits
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
0
0
0
0
0
1
1
1
X
X
X
X
X
X
X
X
sp7
sp6
sp5
sp4
sp3
sp2
sp1
sp0
0
0
0
0
1
0
0
0
X
X
sg1
3
sg1
2
sg1
1
sg1
0
sg9
sg8
sg7
sg6
sg5
sg4
sg3
sg2
sg1
sg0
TRI-STATE REGISTER
comparator on each input remains active. This command
allows the use of each input as a comparator with a 4.0 V
threshold. The MCU may change or update the Tri-state
Register via software at any time in Normal mode.
The tri-state command is use to set the SPn or SGn input
node as high-impedance (refer to Table 10). By setting the
Tri-state Register bit to logic [1], the input will be highimpedance regardless of the metallic command setting. The
Table 10. Tri-state Command
Tri-State Commands
Command Bits
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
0
0
0
0
1
0
0
1
X
X
X
X
X
X
X
X
0
0
0
0
1
0
1
0
X
X
7
6
5
4
3
2
1
0
sp7 sp6 sp5 sp4 sp3 sp2 sp1 sp0
sg13 sg12 sg11 sg10 sg9 sg8 sg7 sg6 sg5 sg4 sg3 sg2 sg1 sg0
ANALOG SELECT REGISTER
selects the input as high-impedance. Setting bit 6 and bit 5 to
0,1 selects 4.0 mA, and 1,0 selects 32 mA. Setting bit 6 and
bit 5 to 1,1 in the Analog Select Register is not allowed and
will place the input as an analog input with high-impedance.
Analog currents set by the analog command are pull-up
currents for all SGn and SPn inputs (refer to Table 11). The
analog command does not allow pull-down currents on the
SPn inputs. Setting the current to 32 or 4.0 mA may be useful
for reading sensor inputs. Further information is provided in
the Typical Applications section of this datasheet beginning
on page 23. The MCU may change or update the Analog
Select Register via software at any time in Normal mode.
The analog voltage on switch inputs may be read by the MCU
using the analog command (refer to Table 11). Internal to the
IC is a 22-to-1 analog multiplexer. The voltage present on the
selected input pin is buffered and made available on the
AMUX output pin. The AMUX output pin is clamped to a
maximum of VDD volts regardless of the higher voltages
present on the input pin. After an input has been selected as
the analog, the corresponding bit in the next SO data stream
will be logic [0]. When selecting a channel to be read as
analog, the user must also set the desired current (32 mA,
4.0 mA, or high-impedance). Setting bit 6 and bit 5 to 0,0
Table 11. Analog Command
Analog Command
Not used
Current
Select
Analog Channel Select
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
0
0
0
0
0
1
1
0
X
X
X
X
X
X
X
X
X
32
mA
4.0
mA
0
0
0
0
0
33975
18
Analog Integrated Circuit Device Data
Freescale Semiconductor
FUNCTIONAL DEVICE OPERATION
OPERATIONAL MODES
Table 12. Analog Channel
Bits 43210
Analog Channel Select
00000
No Input Selected
00001
SG0
00010
SG1
00011
SG2
00100
SG3
00101
SG4
00110
SG5
00111
SG6
01000
SG7
01001
SG8
01010
SG9
01011
SG10
01100
SG11
01101
SG12
01110
SG13
01111
SP0
10000
SP1
10001
SP2
10010
SP3
10011
SP4
10100
SP5
10101
SP6
10110
SP7
CALIBRATION OF TIMERS
oscillator frequency changes with temperature, calibration is
required for an accurate time base. Calibrating the timers has
no affect on the quiescent current measurement. The
calibration command simply makes the time base more
accurate. The calibration command may be used to update
the device on a periodic basis. All reset conditions clear the
calibration register and places the device in the uncalibrated
state.
In cases where an accurate time base is required, the user
may calibrate the internal timers using the calibration
command (refer to Table 13). After the 33975 device
receives the calibration command, the device expects 512 s
logic [0] calibration pulse on the CS pin. The pulse is used to
calibrate the internal clock. No other SPI pins should
transition during this 512 s calibration pulse. Because the
Table 13. Calibration Command
Calibration Command
Command Bits
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
0
0
0
0
1
0
1
1
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
RESET
The reset command resets all registers to Power-ON Reset
(POR) state. Refer to Table , page 20, for POR states or the
paragraph entitled Power-ON Reset (POR) on page 16 of
this datasheet.
33975
Analog Integrated Circuit Device Data
Freescale Semiconductor
19
FUNCTIONAL DEVICE OPERATION
OPERATIONAL MODES
Table 14. Reset Command
Reset Command
Command Bits
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
0
1
1
1
1
1
1
1
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
SPI COMMAND SUMMARY
Output (SO) data for input voltages greater or less than the
threshold level. Open switches are always indicated with a
logic [0], closed switches are indicated with logic [1].
Table below provides a comprehensive list of SPI
commands recognized by the 33975 and the reset state of
each register. Table 16 and Table 17 contain the Serial
Table 15. SPI Command Summar
MSB
Command Bits
Setting Bits
LSBI
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Switch Status
Command
0
0
0
0
0
0
0
0
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Settings
Command
Bat=1, Gnd=0
(Default state = 1)
0
0
0
0
0
0
0
1
X
X
X
X
X
X
X
X
SP7 SP6 SP5 SP4 SP3 SP2 SP1 SP0
Wake-up/Interrupt
Bit
Wake-up=1
Nonwake-up=0
(Default state = 1)
0
0
0
0
0
0
1
0
X
X
X
X
X
X
X
X
SP7 SP6 SP5 SP4 SP3 SP2 SP1 SP0
0
0
0
0
0
0
1
1
X
X
Metallic
Command
Metallic = 1
Non-metallic = 0
(Default state = 1)
0
0
0
0
0
1
0
0
X
X
0
0
0
0
0
1
0
1
X
X
Analog Command
0
0
0
0
0
1
1
0
X
X
Wetting Current
Timer
Enable Command
Timer ON = 1
Timer OFF = 0
(Default state = 1)
0
0
0
0
0
1
1
1
X
X
0
0
0
0
1
0
0
0
X
X
Tri-state
Command
Input Tri-state=1
0
0
0
0
1
0
0
1
X
X
0
0
0
0
1
0
1
0
X
X
Calibration
Command
(Default state uncalibrated)
0
0
0
0
1
0
1
1
X
X
X
X
X
X
X
X
X
X
Sleep Command
(See Sleep Mode
on page 21)
0
0
0
0
1
1
0
0
X
X
X
X
X
X
X
X
X
X
Reset Command
0
1
1
1
1
1
1
1
X
X
X
X
X
X
X
X
X
X
SG1 SG1 SG1 SG1 SG9 SG8 SG7 SG6 SG5 SG4 SG3 SG2 SG1 SG0
3
2
1
0
X
X
X
X
X
X
SP7 SP6 SP5 SP4 SP3 SP2 SP1 SP0
SG1 SG1 SG1 SG1 SG9 SG8 SG7 SG6 SG5 SG4 SG3 SG2 SG1 SG0
3
2
1
0
X
X
X
X
X
X
X
X
X
X
X
X
X
32m 4.0
A
mA
0
0
0
0
0
0
0
SP7 SP6 SP5 SP4 SP3 SP2 SP1 SP0
SG1 SG1 SG1 SG1 SG9 SG8 SG7 SG6 SG5 SG4 SG3 SG2 SG1 SG0
3
2
1
0
X
X
X
X
X
X
SP7 SP6 SP5 SP4 SP3 SP2 SP1 SP0
SG1 SG1 SG1 SG1 SG9 SG8 SG7 SG6 SG5 SG4 SG3 SG2 SG1 SG0
3
2
1
0
X
X
X
X
X
X
int
int
int sca sca sca
n
n
time time time n
time time time
r
r
r
r
r
r
X
X
X
X
X
X
SO Response Will ther RST SP7 SP6 SP5 SP4 SP3 SP2 SP1 SP0 SG1 SG1 SG1 SG1 SG9 SG8 SG7 SG6 SG5 SG4 SG3 SG2 SG1 SG0
Always Send
m
3
2
1
0
flg
flg
33975
20
Analog Integrated Circuit Device Data
Freescale Semiconductor
FUNCTIONAL DEVICE OPERATION
OPERATIONAL MODES
Table 16. Serial Output (SO) Bit Data
Type of Input
Input
Programmed
Voltage on Input
Pin
SO SPI Bit
SP
Switch to Ground
SPn < 4.0 V
1
Switch to Ground
SPn > 4.0 V
0
Switch to Battery
SPn < 4.0 V
0
Switch to Battery
SPn > 4.0 V
1
N/A
SGn < 4.0 V
1
N/A
SGn > 4.0 V
0
SG
Table 17. Serial Output (SO) Response Register
SO Response
Will
Always Send
ther RST SP7 SP6 SP5 SP4 SP3 SP2 SP1 SP0 SG1 SG1 SG1 SG1 SG9 SG8 SG7 SG6 SG5 SG4 SG3 SG2 SG1 SG0
m
3
2
1
0
flg
flg
EXAMPLE OF NORMAL MODE OPERATION
The operation of the device in Normal mode is defined by the
states of the programmable internal control registers. A
typical application may have the following settings:
• Programmable switch – set to switch-to-ground
• All inputs set as wake-up
• Wetting current on (32 mA)
• Wetting current timer on (20 ms)
• All inputs tri-state-disabled (comparator is active)
• Analog select 00000 (no input channel selected)
With the device programmed as above, an interrupt will be
generated with each switch contact change of state (open-toclose or close-to-open) and 32 mA of contact wetting current
will be source for 20 ms. The INT pin will remain low until
switch status is acknowledged by the microprocessor. It is
critical to understand INT will not be cleared on the rising
edge of CS if a switch closure occurs while the CS is low. The
maximum duration a switch state change can exist without
acknowledgement depends on the software response time to
the interrupt. Figure 6, page 11, shows the interaction
between changing input states and the INT and CS pins.
If desired the user may disable interrupts (wake-up/interrupt
command) from the 33975 device and read the switch states
on a periodic basis. Switch activation and deactivation faster
than the MCU read rate will not be acknowledged.
The 33975 device will exit the Normal mode and enter the
Sleep mode only with a valid sleep command.
SLEEP MODE
Sleep mode is used to reduce system quiescent currents.
Sleep mode may be entered only by sending the sleep
command. All register settings programmed in Normal mode
will be maintained in Sleep mode.
The 33975 will exit Sleep mode and enter Normal mode when
any of the following events occur:
• Input switch change of state (when enabled)
• Interrupt timer expire
• Falling edge of WAKE
• Falling edge of INT (with VDD = 5.0 V and WAKE at
Logic [1])
• Falling edge of CS (with VDD = 5.0 V)
• Power-on reset (POR)
The VDD supply may be removed from the device during
Sleep mode. However removing VDD from the device in
Sleep mode will disable a wake-up from falling edge of INT
and CS.
Note: In cases where CS is used to wake the device, the first
SO data message is not valid.
The sleep command contains settings for two programmable
timers for Sleep mode, the interrupt timer and the scan timer,
as shown in Table 18.
Table 18. Sleep Command
Sleep Command
Command Bits
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
0
0
0
1
1
0
0
X
X
X
X
X
X
X
X
X
X
int timer
int timer
int timer
scan timer
scan timer
0
scan timer
23
33975
Analog Integrated Circuit Device Data
Freescale Semiconductor
21
FUNCTIONAL DEVICE OPERATION
OPERATIONAL MODES
The interrupt timer is used as a periodic wake-up timer. When
the timer expires, an interrupt is generated and the device
enters Normal mode.
Note: The interrupt timer in the 33975 device may be
disabled by programming the interrupt bits to logic [1 1 1].
Table 19 shows the programmable settings of the Interrupt
timer.
The scan timer sets the polling period between input switch
reads in Sleep mode. The period is set in the sleep command
and may be set to 000 (no period) to 111 (64 ms). In Sleep
mode when the scan timer expires, inputs will behave as
programmed prior to sleep command. The 33975 will wake
up for approximately 125 s and read the switch inputs. At
the end of the 125 s, the input switch states are compared
with the switch state prior to sleep command. When switch
state changes are detected, an interrupt (when enabled; refer
to wake-up/interrupt command description on page 17) is
generated and the device enters Normal mode. Without
switch state changes, the 33975 will reset the scan timer,
inputs become tri-state, and the Sleep mode continues until
the scan timer expires again.
Table 20 shows the programmable settings of the Scan
timer.
Note: The interrupt and scan timers are disabled in the
Normal Mode.
Figure 5, page 11, is a graphical description of how the
33975 device exits Sleep mode and enters Normal mode.
Notice that the device will exit Sleep mode when the interrupt
timer expires or when a switch change of state occurs. The
falling edge of INT triggers the MCU to wake from Sleep state.
Figure 12 illustrates the current consumed during Sleep
mode. During the 125 s, the device is fully active and switch
states are read. The quiescent current is calculated by
integrating the normal running current over scan period plus
approximately 60 A.
I=V/R oror0.270V/100ohm
= 2.7mA
I=V/R
0.270V/100=2.7mA
Inputs active for
Inputs active for 125 us
125s
out
of 32 out
ms of 32ms
I=V/R or
I=V/R
or6mV/100ohm = 60 uA
6.0mV/100=60A
Table 19. Interrupt Timer
Figure 12. Sleep Current Waveform
Bits 543
Interrupt Period
000
32 ms
TEMPERATURE MONITOR
001
64 ms
010
128 ms
011
256 ms
100
512 ms
101
1.024 s
110
2.048 s
111
No interrupt wake-up
With multiple switch inputs closed and the device
programmed with the wetting current timers disabled,
considerable power will be dissipated by the IC. For this
reason temperature monitoring has been implemented. The
temperature monitor is active in the Normal mode only. When
the IC temperature is above the thermal limit, the temperature
monitor will do all of the following:
• Generate an interrupt.
• Force all wetting current sources to revert to 2.0 mA/
4.0 mA sustain currents
• Maintain the 2.0 mA/4.0 mA sustain currents and all
other functionality.
• Set the thermal flag bit in the SPI output register.
The thermal flag bit in the SPI word will be cleared on the
rising edge of CS provided the die temperature has cooled
below the thermal limit. When die temperature has cooled
below thermal limit, the device will resume previously
programmed settings.
Table 20. Scan Timer
Bits 210
Scan Period
000
No Scan
001
1.0 ms
010
2.0 ms
011
4.0 ms
100
8.0 ms
101
16 ms
110
32 ms
111
64 ms
33975
22
Analog Integrated Circuit Device Data
Freescale Semiconductor
TYPICAL APPLICATIONS
OPERATIONAL MODES
TYPICAL APPLICATIONS
The 33975’s primary function is the detection of open or
closed switch contacts. However, there are many features
that allow the device to be used in a variety of applications.
The following is a list of applications to consider for the IC:
• Sensor power supply
• Switch monitor for metallic or elastomeric switches
• Analog sensor inputs (Ratiometric)
• Power MOSFET/LED driver and monitor
• Multiple 33975 devices in a module system
The following paragraphs describe the applications in detail.
SENSOR POWER SUPPLY
Each input may be used to supply current to sensors external
to a module. Many sensors such as Hall effect, pressure
sensors, and temperature sensors require a supply voltage to
power the sensor, and provide an open collector or analog
output. Figure 13 shows how the 33975 may be used to
supply power and interface to these types of sensors. In an
application where the input makes continuous transitions,
consider using the wake-up/interrupt command to disable
the interrupt for the particular input.
33975
VBAT
SP0
SP1
VPWR
VDD
MCU
VDD
VBAT
SP7
WAKE
SG0
SG1
VPWR VPWR
32
mA
32 mA
4.0
mA
SI
MOSI
SCLK
CS
SCLK
SO
MISO
INT
INT
CS
Metallic switch contacts often develop higher contact
resistance over time owing to contact corrosion. The
corrosion is induced by humidity, salt, and other elements
that exist in the environment. For this reason the 33975
provides two settings for contacts. When programmed for
metallic switches, the device provides higher wetting current
to keep switch contacts free of oxides. The higher current
occurs for the first 20 ms of switch closure. Where longer
duration of wetting current is desired, the user may send the
wetting current timer command and disable the timer. Wetting
current will be continuous to the closed switch. After the time
period set by the MCU, the wetting current timer command
may be sent again to enable the timer. The user must
consider power dissipation on the device when disabling the
timer. (Refer to the paragraph entitled Temperature Monitor,
page 22.)
To increase the amount of wetting current for a switch
contact, the user has two options. Higher wetting current to a
switch may be achieved by paralleling SGn or SPn inputs.
This will increase wetting current by 32 mA for each input
added to the switch-to-ground contact and 16 mA for switchto-battery contacts. The second option is to simply add an
external resistor pull-up to the VPWR supply for switch-toground inputs or a resistor to ground for a switch-to-battery
input. Adding an external resistor has no effect on the
operation of the device.
Elastomeric switch contacts are made of carbon and have a
high contact resistance. Resistance of 1.0 k is common. In
applications with elastomeric switches, the pull-up and pulldown currents must be reduced to prevent excessive power
dissipation at the contact. Programming for a lower current
settings is provided in the Functional Device Operation
Section beginning on page 16 under Table 8, Metallic
Command.
SG12
ANALOG SENSOR INPUTS (RATIOMETRIC)
VPWR VPWR
Hall-Effect
Sensor
Reg
METALLIC/ELASTOMERIC SWITCH
32
mA
SG13
4.0
mA
IOC[7:0]
AMUX
Input Capture
Timer Port
X
VDD
VPWR
0V
0V
SG13
AMUX
Figure 13. Sensor Power Supply
The 33975 features a 22-to-1 analog multiplexer. Setting the
binary code for a specific input in the analog command allows
the microcontroller to perform analog to digital conversion on
any of the 22 inputs. On rising edge of the CS, the multiplexer
connects a requested input to the AMUX pin. The AMUX pin
is clamped to max of VDD volts regardless of the higher
voltages present on the input pin. After an input has been
selected as the analog, the corresponding bit in the next SO
data stream will be logic [0].
The input pin, when selected as analog, may be configured
as analog with high-impedance, analog with 4.0 mA pull-up,
or analog with 32 mA pull-up. Figure 14, page 24, shows how
the 33975 may be used to provide a ratiometric reading of
variable resistive input.
33975
Analog Integrated Circuit Device Data
Freescale Semiconductor
23
TYPICAL APPLICATIONS
OPERATIONAL MODES
33975
VBAT
SP0
SP1
ADC =
VPWR
VDD
MCU
VDD
VBAT
SP7
32
mA
I1
4.0mA
VPWR VPWR
4.0
mA
SG12
SI
MOSI
SCLK
SCLK
CS
CS
SO
MISO
INT
INT
AMUX
VPWR VPWR
R1
32
Analog Sensor
or Analog Switch mA
SG13
I2
4.0mA
1.21k
0.1%
4.0
mA
4.0mA x 1.0k
4.0mA x 1.21k
AN0
Analog
Ports
Using the equation yields the following:
The ADC value of 213 counts is the value with 0% error
(neglecting the resistor tolerance and AMUX input offset
voltage). Now calculate the count value induced by the
mismatch in current sources. From a sample device the
maximum current source was measured at 3.979 mA and
minimum current source was measured at 3.933 mA. This
yields 1.16% error in A/D conversion due to the current
source mismatch. The A/D measurement will be as follows:
4.36V to 5.32V
R2
x 255
ADC = 210 counts
WAKE
SG0
SG1
ADC =
I1 x R1
x 255
I2 x R2
VREF(H)
VREF(L)
Figure 14. Analog Ratiometric Conversion
To read a potentiometer sensor, the wiper should be
grounded and brought back to the module ground, as
illustrated in Figure 14. With the wiper changing the
impedance of the sensor, the analog voltage on the input will
represent the position of the sensor.
Using the Analog feature to provide 4.0 mA of pull-up current
to an analog sensor may induce error due to the accuracy of
the current source. For this reason, a ratiometric conversion
must be considered. Using two current sources (one for the
sensor and one to set the reference voltage to the A/D
converter) will yield a maximum error (owing to the 33975) of
4%.
Higher accuracy may be achieved through module level
calibration. In this example, we use the resistor values from
Figure 14 and assume the current sources are 4% from each
other. The user may use the module end-of-line tester to
calculate the error in the A/D conversion. By placing a
1.0 k, 0.1% resistor in the end-of-line test equipment and
assuming a perfect 4.0 mA current source from the 33975, a
calculated A/D conversion may be obtained.
ADC =
3.933 mA x 1.0k
3.979 mA x 1.21k
x 255
ADC = 208 counts
This A/D conversion is 1.16% low in value. The error
correction factor of 1.0115 may be used to correct the value:
ADC = 208 counts x 1.0116
ADC = 210 counts
An error correction factor may then be stored in E2 memory
and used in the A/D calculation for the specific input. Each
input used as analog measurement will have a dedicated
calibrated error correction factor.
POWER MOSFET/LED DRIVER AND MONITOR
Because of the flexible programming of the 33975 device, it
may be used to drive small loads like LEDs or MOSFET
gates. It was specifically designed to power up in the Normal
Mode with the inputs tri-state. This was done to ensure the
LEDs or MOSFETs connected to the 33975 power up in the
off-state. The Switch Programmable (SP0–SP7) inputs have
a source-and-sink capability, providing effective MOSFET
gate control. To complete the circuit, a pull-down resistor
should be used to keep the gate from floating during the
Sleep Modes. Figure 15, page 25, shows an application
where the SG0 input is used to monitor the drain-to-source
voltage of the external MOSFET. The 750 resistor is used
to set the drain-to-source trip voltage. With the 4.0 mA
current source enabled, an interrupt will be generated when
the drain-to-source voltage is approximately 1.0 V.
33975
24
Analog Integrated Circuit Device Data
Freescale Semiconductor
TYPICAL APPLICATIONS
OPERATIONAL MODES
current to the 750 resistor, the analog voltage on the SGn
pin will be approximately:
VBAT
LOAD
VPWR VPWR
32
mA
750
SG0
VSGn = ISGn x 750 + VDS
4.0
mA
SG0
AMUX
100k
4.0 V Ref
+
-
To SPI
Comparator
VPWR VPWR
32
mA
SG0
4.0
mA
SP0
To SPI
4.0 V +Ref
Comparator
2.0 mA
16
mA
VPWR VPWR
32
mA
SG13
4.0
mA
SG13
4.0 V Ref
+
-
To SPI
Comparator
Figure 15. MOSFET or LED Driver Output
The sequence of commands (from Normal mode with inputs
tri-state) required to set up the device to drive a MOSFET are
as follows:
• wetting current timer enable command –Disable SPn
wetting current timer (refer to Table 9, page 18).
• metallic command –Set SPn to 16/32 mA or 2.0/4.0 mA
gate drive current (refer to Table 8, page 17).
• settings command –Set SPn as switch-to-battery (refer
to Table 6, page 16).
• tri-state command –Disable tri-state for SPn (refer to
Table 10, page 18).
After the tri-state command has been sent (tri-state disable),
the MOSFET gate will be pulled to ground. From this point
forward the MOSFET may be turned on and off by sending
the settings command:
• settings command –SPn as switch-to-ground
(MOSFET ON).
• settings command –SPn as switch-to-battery
(MOSFET OFF).
Monitoring of the MOSFET drain in the OFF state provides
open load detection. This is done by using an input
comparator. With the SGn input in tri-state, the load will pull
up the input to battery. With the load open, the SGn pin is
pulled down to ground through an external resistor. The open
load is indicated by a logic [1] in the SO data bit.
The analog command may be used to monitor the drain
voltage in the MOSFET ON state. By sourcing 4.0 mA of
As the voltage on the drain of the MOSFET increases, so
does the voltage on the SGn pin. With the SGn pin selected
as analog, the MCU may perform the A/D conversion.
Using this method for controlling unclamped inductive loads
is not recommended. Inductive fly-back voltages greater than
VPWR may damage the IC.
The SP0–SP7 pins of this device may also be used to send
signals from one module to another. Operation is similar to
the gate control of a MOSFET.
For LED applications a resistor in series with the LED is
recommended but not required. The switch-to-ground inputs
are recommended for LED application. To drive the LED use
the following commands:
• wetting current timer enable command –Disable SGn
wetting current timer.
• metallic command –Set SGn to 32 mA.
From this point forward the LED may be turned on and off
using the tri-state command:
• tri-state command –Disable tri-state for SGn (LED ON).
• tri-state command –Enable tri-state for SGn (LED
OFF).
These parameters are easily programmed via SPI
commands in Normal mode.
Multiple 33975 Devices in a Module System
Connecting power to the 33975 and the MCU for Sleep mode
operation may be done in several ways. Table 21 shows
several system configurations for power between the MCU
and the 33975 and their specific requirements for
functionality.
Table 21. Sleep Mode Power Supply
MCU
VDD
33975
VDD
Comments
5.0V
5.0V
All wake-up conditions apply. (Refer to Sleep
Mode, page 21.)
5.0V
0V
0V
5.0V
0V
0V
SPI wake-up is not possible.
Sleep mode is not possible. Current from the CS
pull-up will flow through the MCU to the VDD
that has been switched off. The negative edge
of CS will put 33975 in Normal mode.
SPI wake-up is not possible.
Multiple 33975 devices may be used in a module system. SPI
control may be done in parallel or serial. However when
parallel mode is used, each device is addressed
independently (refer to MCU Interface Description, page 15).
33975
Analog Integrated Circuit Device Data
Freescale Semiconductor
25
TYPICAL APPLICATIONS
OPERATIONAL MODES
Therefore, when sending the sleep command, one device will
enter sleep before the other. For multiple devices in a system,
it is recommended that the devices are controlled in serial (S0
from first device is connected to SI of second device). With
two devices, 48 clock pulses are required to shift data in.
When the WAKE feature is used to enable the power supply,
both WAKE pins should be connected to the enable pin on the
power supply. The INT pins may be connected to one
interrupt pin on the MCU, or may have their own dedicated
interrupt to the MCU.
The transition from Normal to Sleep mode is done by sending
the sleep command. With the devices connected in serial and
the sleep command sent, both will enter Sleep mode on the
rising edge of CS. When Sleep mode is entered, the WAKE
pin will be logic [1]. If either device wakes up, the WAKE pin
will transition low, waking the other device.
A condition exists where the MCU is sending the sleep
command (CS logic [0]) and a switch input changes state.
With this event, the device that detects this input will not
transition to Sleep mode, while the second device will enter
Sleep mode. In this case, two switch status commands must
be sent to receive accurate switch status data. The first
switch status command will wake the device in Sleep mode.
Switch status data may not be valid from the first switch
status command because of the time required for the input
voltage to rise above the 4.0 V input comparator threshold.
This time is dependant on the impedance of SGn or SPn
node. The second switch status command will provide
accurate switch status information. It is recommended that
the software wait 10 to 20 ms between the two switch status
commands, allowing time for switch input voltages to
stabilize. With all switch states acknowledged by the MCU,
the sleep sequence may be initiated. All parameters for Sleep
mode should be updated prior to sending the sleep
command.
The 33975 IC has an internal 5.0 V supply from the VPWR
pin. A POR circuit monitors the internal 5.0 V supply. In the
event of transients on the VPWR pin, an internal reset may
occur. Upon reset the 33975 will enter Normal mode with the
internal registers as defined in Table , page 20. Therefore it
is recommended that the MCU periodically update all
registers internal to the IC.
USING THE WAKE FEATURE
The 33975 provides a WAKE output and wake-up input
designed to control an enable pin on system power supply.
While in the Normal mode, the WAKE output is low, enabling
the power supply. In the Sleep mode, the WAKE pin is high,
disabling the power supply. The WAKE pin has a passive pullup to the internal 5.0 V supply but may be pulled up through
a resistor to VPWR supply (see Figure 17, page 27).
When the WAKE output is not used the pin should be pulled
up to the VDD supply through a resistor, as shown in
Figure 16, page 27).
During the Sleep mode, a switch closure will set the WAKE
pin low, causing the 33975 to enter the Normal mode. The
power supply will then be activated, supplying power to the
VDD pin and the microprocessor and the 33975. The
microprocessor can determine the source of the wake-up by
reading the interrupt flag.
COST AND FLEXIBILITY
Systems requiring a significant number of switch interfaces
have many discrete components. Discrete components on
standard PWB consume board space and must be checked
for solder joint integrity. An integrated approach reduces
solder joints, consumes less board space, and offers wider
operating voltage, analog interface capability, and greater
interfacing flexibility.
33975
26
Analog Integrated Circuit Device Data
Freescale Semiconductor
TYPICAL APPLICATIONS
OPERATIONAL MODES
DD
VBAT
Power
Supply
VDD
33975
VBAT
VPWR
VPWR
SP0
SP1
VDD
VBAT
VDD
SP7
MC68HCXX
Microprocessor
WAKE
SG0
SG1
SG12
CS
CS
INT
INT
SI
MOSI
SO
MISO
SCLK
SCLK
AMUX
AN0
SG13
Figure 16. Power Supply Active in Sleep Mode
VBAT
Power
Supply
33975
VBAT
VPWR
VDD
Enable
VPWR
SP0
SP1
WAKE
VBAT
VDD
VDD
MC68HCXX
Microprocessor
SP7
SG0
SG1
CS
CS
INT
INT
SI
MOSI
SO
MISO
SCLK
SCLK
AMUX
SG12
AN0
SG13
Figure 17. Power Supply Shutdown in Sleep Mode
33975
Analog Integrated Circuit Device Data
Freescale Semiconductor
27
PACKAGING
PACKAGE DIMENSIONS
PACKAGING
PACKAGE DIMENSIONS
Important: For the most current revision of the package, visit www.freescale.com and perform a “keyword” search on the “98A”
number listed below.
EK SUFFIX
32-PIN EXPOSED PAD
98ASA10556D
REVISION D
33975
28
Analog Integrated Circuit Device Data
Freescale Semiconductor
PACKAGING
PACKAGE DIMENSIONS (CONTINUED)
PACKAGE DIMENSIONS (Continued)
EK SUFFIX
32-PIN EXPOSED PAD
98ASA10556D
REVISION D
33975
Analog Integrated Circuit Device Data
Freescale Semiconductor
29
PACKAGE DIMENSIONS (CONTINUED)
EK SUFFIX
32-PIN EXPOSED PAD
98ASA10556D
REVISION D
33975
30
Analog Integrated Circuit Device Data
Freescale Semiconductor
REVISION HISTORY
REVISION HISTORY
Revision
5.0
Date
6/2007
Description of Changes
•
•
•
•
•
•
6.0
11/2007
•
•
Implemented Revision History page
Updated to Freescale form and style
Added MCZ33975EK/R2 and MCZ33975AEK/R2
Removed Peak Package Reflow Temperature During Reflow, and added Peak Package
Reflow Temperature During Reflow(5), (6)
Removed MC33975AEK/R2 from the Ordering Information
Replaced figures for 33975 Simplified Application Diagram, Power Supply Active in
Sleep Mode, and Power Supply Shutdown in Sleep Mode.
Adjusted ESD voltages for Human Body Model(2) and Applies to all non-input Pins.
Updated document form and style.
7.0
2/2008
• Minor changes to text
8.0
8/2008
• Updated package drawing
9.0
8/2008
• Revised wording of Features on Page 1 - No parameter /technical changes.
10.0
8/2011
11.0
01/2014
• Revised Ordering Information table by adding part numbers MC33975TEK/R2 and
MC33975ATEK/R2, and removing part numbers MC33975EK/R2, MCZ33975EK/R2
and MCZ33975AEK/R2.
• Updated document form and style.
• No technical changes. Revised back page. Updated document properties. Added
SMARTMOS sentence to last paragraph.
33975
Analog Integrated Circuit Device Data
Freescale Semiconductor
31
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Document Number: MC33975
Rev 11.0
01/2014
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